chore: rename generic slots variable

[henryiii]

Description

Fix#5788. Make it a bit easier to interface with Qt code. Qt's terrible macro names strike again.

Suggested changelog entry:

• Rename internal variables to avoid the word slots (reads better)

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📚 Documentation preview 📚: https://pybind11--5793.org.readthedocs.build/

[henryiii]

Getting this on 3.13t pretty often:

FAILED ../../tests/test_gil_scoped.py::test_run_in_process_one_thread[test_callback_std_func] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.
FAILED ../../tests/test_gil_scoped.py::test_run_in_process_one_thread[test_cross_module_gil_inner_pybind11_released] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.
FAILED ../../tests/test_gil_scoped.py::test_run_in_process_multiple_threads_sequential[test_multi_acquire_release_cross_module] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.
FAILED ../../tests/test_gil_scoped.py::test_run_in_process_direct[test_cross_module_gil_inner_custom_released] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.
FAILED ../../tests/test_gil_scoped.py::test_run_in_process_direct[test_cross_module_gil_inner_custom_acquired] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.

[rwgk]

Getting this on 3.13t pretty often:

FAILED ../../tests/test_gil_scoped.py::test_run_in_process_one_thread[test_callback_std_func] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.
FAILED ../../tests/test_gil_scoped.py::test_run_in_process_one_thread[test_cross_module_gil_inner_pybind11_released] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.
FAILED ../../tests/test_gil_scoped.py::test_run_in_process_multiple_threads_sequential[test_multi_acquire_release_cross_module] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.
FAILED ../../tests/test_gil_scoped.py::test_run_in_process_direct[test_cross_module_gil_inner_custom_released] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.
FAILED ../../tests/test_gil_scoped.py::test_run_in_process_direct[test_cross_module_gil_inner_custom_acquired] - RuntimeError: DEADLOCK, most likely, exactly what this test is meant to detect.

Yeah ... it used to be rare until about a month ago, but suddenly this particular test

CI / 🐍 (macos-13, 3.13t, -DCMAKE_CXX_STANDARD=11)

started failing very often. I don't know why, but I believe almost certainly this is unrelated to changes in pybind11.

Maybe there was a Python 3.13 patch release? Or the macOS runners had some change?

If nobody has time to drill down (I don't), maybe we should just disable those tests under macOS with free-threading?

[rwgk]

It wasn't quite a month ago, this was the first time I noticed, July 28, 2025:

#5776 (comment)

[Osyotr]

This is probably not enough to fix the original problem.
https://github.com/python/cpython/blob/0607fdd56c7c5e7f0949f9a6ef95609e9437b1eb/Include/object.h#L509

[rwgk]

This is probably not enough to fix the original problem. https://github.com/python/cpython/blob/0607fdd56c7c5e7f0949f9a6ef95609e9437b1eb/Include/object.h#L509

That's in the cpython sources. There is nothing we can do about that, but I'd vote for merging @Henriii's changes, they make the naming better in general.

[henryiii]

You tagged the wrong henryiii, FYI :)